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AQA A Level Biology > 3.3 Organisms exchange substances with their environment > Flashcards

3.3 Organisms exchange substances with their environment Flashcards

1
Q

What is relationship between the size of organism and its SA:V

A

Smaller organisms tend to have a higher SA:V

Larger organisms have a lower SA:V

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2
Q

What is the relationship between the SA:V and metabolic rate

A

Rate of heat loss higher in smaller animals than larger
Due to high SA:V
METABOLLIC RATE HIGHER —> faster respiration
To generate enough heat to maintain constans body temperature

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3
Q

Why is gas exchange important?

A

O2 supply = production of ATP for biochemical reactions
Removal of Co2 = toxic waste product of aerobic respiration
It builds in cells, PH is altered

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4
Q

What are the adaptations of gas exchange surfaces?

A

Thin, flat shape
Large SA:V
Short diffusion pathway
= rapid diffusion

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5
Q

Describe the gas exchange in Insects

A
  1. Air moves through spiracles (pores) on the surface of the insect
  2. Air moves through tracheae
  3. Gas exchange at tracheoles directly to/from cells
    Oxygen diffuses down conc. gradient to respiring cell
    Carbon dioxide diffuses down conc. gradient from respiring cells
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6
Q

What are the adaptations in the tracheal system for efficient gas exchange

A

Thin branching tracheoles → short diffusion pathway

Abdonminal contractions of muscles → mass movement → increase in exchange of respiratory gaeses

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7
Q

What are the limitations of tracheal system?

A

Relies on exchange of gases w/envrionment
Diffusion pathway must be short
Pathway limit = limits their overall insect size

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8
Q

Explain the counter-current flow

A

Countercurrent flow
Opposite directions of blood and water flowing
There is always a higher concentration of oxygen in water than blood
Concentration gradient of oxygen between the water and blood is maintained along whole length of lamellae
Equilibrium not met

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9
Q

Describe the adaptations in the fish for gas exchange

A

Countercurrent flow = maintains large concentration gradient
Gill filaments + Gill lamallae → provide a larger surface aea
Network of capillaries (on lamellae) → remove oxygen to maintain concentration gradient
Thin epithelium → shorter diffusion pathway between water and blood

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10
Q

What is the process of gas exchange in leaves of dicotyledonous plants?

A

Carbon dioxide diffuses int through the stomota
Stomata opened by the guard cells
Carbon dioxide diffuse into mesophyll layer into air spaces
Carbon dioxide diffuses down concentration gradient
Oxygen diffuses out while Carbon diffuses in

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11
Q

What are the adaptions in plants for efficient gas exchange?

A

Lots of Stomata → large surface area due to being close together
Mesophyll cells have a large surface area → rapid diffusion of gases
Thin → short diffusion pathway

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12
Q

Describe the xerophytic adaptations for efficient gas exchange and the limitation of water loss

A
  • Thick waxy cuticle = Increases diffusion distance → less evaporation
  • Stomata in pits/grooves = ‘Trap’ water vapour → water potential gradient
    decreased → less evaporation
  • Rolled leaves = ‘Trap’ water vapour → water potential gradient decreased → less evaporation
  • Spindles/needles = Reduces surface area to volume ratio
  • Hairs = ‘Trap’ water vapour → water potential gradient decreased → less evaporation
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13
Q

What adaptations in terrestrial insects limit water loss

A

Thick waxy cuticle → increases diffusion distance = less evaporation

Spricales can open and close → open to allow oxygen in, close when water loss too much

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14
Q

How does gas exchange occur in the alveoli?

A
  • Oxygen diffuses from alveoli
  • Down its concentration gradient
  • Across the alveolar epithelium
  • Across the capillary endothelium
  • Into the blood (in haemoglobin)
  • Carbon dioxide diffuses from capillary
  • Down its concentration gradient
  • Across the capillary endothelium
  • Across the alveolar epithelium
  • Into the alveoli
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15
Q

Why is ventilation important?

A

Maintains an oxygen concentration gradient

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16
Q

Why do humans need a large intake of oxygen and removal of carbon dioxide?

A

Large organisms w/ large volume

Need to maintain body temp

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17
Q

How do the tracheal rings provide support?

A

Made of cartilage which help support trachea and stays open

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18
Q

How has alveoli adapted for the exchange of gases in humans?

A

Large number = higher surface area
Alveolar epithelium and capillary (endothelial) is one cell thick - short diffusion pathway
Movement of blood in the capillaries = maintain a concentration gradient

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19
Q

Describe the lining of the trachea

A

Ciliated epithelium

Contains goblet cells that can secrete mucus

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20
Q

Where does the exchange of oxygen take place in a human?

A

Between alveoli and the capillaries in the lung

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21
Q

What is ventilation?

A

The processes by which air in constantly moved in and out of the lungs

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22
Q

Describe Inspiration (inhalation)

A

Active process
External intercostal muscles contract (internal relax)
Causing ribcage to move upwards and out ( increased volume in thorax)
Diaphragm muscles contract = flatten = volume increase
Volume in thorax cavity increasing leads to less pressure in lungs
Atmospheric pressure is greater than in lungs so diffusion gradient into the lungs

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23
Q

Describe Expiration

A

Passive
The internal intercostal muscles contract (external relax)
Ribs move downwards and inwards = decreases the volume of the thorax
Diaphragm muscles relax and become dome-shaped = decrease in volume
A decrease in thorax cavity volume leads to an increase in pressure
Pulmonary pressure is greater than atmospheric = air forced out

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23
Q

How does Expiration affect the lungs?

A

Volume in the chest decreases and pressure increases

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24
Q

How would you describe the relationship between the intercostal muscles?

A

Antagonistic interaction

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25
Q

What is PVR stand for in terms of breathing?

A

The Pulmonary Ventilation Rate is the volume of breathed, in or out, in a minute

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26
Q

How can you calculate the PVR?

A

Tidal volume x Breathing rate

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27
Q

What can breathing be seen as in support of the diffusion of oxygen and carbon dioxide?

A

A form of mass transport (= acts as external medium over the surface)

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28
Q

How does breathing help the diffusion of gases between alveoli and blood?

A

Constant ventilation
Constant circulation of blood
Steep concentration gradient

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29
Q

How do red blood cells help themselves in the diffusion between the alveloi?

A

They flatten against capillary walls so short diffusion pathway

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30
Q

Describe how lung disease causes damage to lungs

A

Tumour formed
Uncontrolled mitosis which develops in cells in the lumen
Interferes with lung system = squeeze blood vessels and entering the lymphatic system

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31
Q

What are the symptoms of lung disease?

A

Coughing up blood
Coughing alot of mucus
Persistent cough
back/shoulder pain

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32
Q

What does COPD stand for?

A

Chronic Obstructive Pulmonary Disease

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33
Q

What are three ways to measure volumes of air involved in gas exchange?

A

Three-way taps, manometers and simple respirometers

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34
Q

What is fibrosis?

A

Formation of scar tissue in the lungs (as a result of infection/exposure to substances)

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35
Q

Explain how fibrosis affects the lungs

A
  1. Scar tissue forms from infection or exposure to asbestos/ dust
  2. Scar tissue is thicker and less elastic than normal lung tissue
    - Diffusion distance increased due to short diffusion pathway
  3. Therefore lungs less able to expand, therefore can’t hold as much air
  4. therefore TV and FVC decreased

(Symptoms = shortness of breath, dry cough, chest pain, fatigue)

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36
Q

Describe an asthma attack

A

constriction of the airways, = narrower diameter meaning reduced air flow.
FEV reduced
Less oxygen enters alveoli enters the blood
Therefore volume of air that can be breathed out decreases

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37
Q

Define emphysema

A

Lung disease caused by smoking or exposure to air pollution (pollutants get trapped in aleveoli)

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38
Q

Describe emphysema’s effect on the lung

A

Particles trapped in the alveoli
Causes inflammation = attracts phagocytes
Phagocytes make an enzyme that beaks from elastin
Loss of elasticity means cannot ventilate properly and loss of surface area
Shortness of breath as they try to compensate the loss

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39
Q

Why do people with lung diseases show symptoms of weakness, fatigue, etc.

A 
Reduce rate of gas exchange in alveoli → less oxygen diffuse into blood → 
cells receive less oxygen → 
rate of aerobic respiration reduced → 
less energy released →
 fatigue, weakness etc.
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40
Q

Define digestion

A

The process in which large molecules are hydrolysed by enzymes into small molecules which can be absorbed or assimilated

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41
Q

Describe Amylase

A

Enzyme that is made in the salivary and the pancreas

42
Q

What are the two stages of digestion?

A

Physical Breakdown and Chemical Digestion

43
Q

What are the two stages of digestion?

A

Physical Breakdown and Chemical Digestion

44
Q

How is the physical breakdown of food good?

A

Provides Larger Surface Area for chemical digestion

45
Q

Describe the digestion of starch

A

Amylase produced by salivary glands in mouth
Amylase hydrolyses starch to maltose (polysaccharide to disaccharide)
Acidic nature of stomach denatures salivary amylase
Membrane bound maltase (attached to epithelial cells lining the ileum of the small intestine) → hydrolyses maltose to glucose (disaccharide to monosacccharide)
Hydrolysis of glycosidic bond

46
Q

Digestion of disaccharides

A

Membrane bound disaccharidases ( maltase, sucrose, lactase) → hydrolyses disaccharide to x2 named monosachhrides

Hydrolysis of glycosidic bond

47
Q

Describe the digestion of lipids by lipase, including action of bile salts

A

Bile salts produced by the liver
Bile salts emulsify lipids into (smaller droplets)
INCREASES SURFACE AREA:VOLUME RATIO = lipases work faster

Lipase made in the pancreas, released in small intestine
Lipase hydroylses lipids → monogylcerides + fatty acids
Breaking ester bond
Monogylcerides, fatty acids and bile salts stick together to form micelles

48
Q

Describe the digestion of proteins by Endopeptidases

A

Hydrolyse peptide bonds between amino acids in a protien

Breakdown of protein into two or more smaller peptides

49
Q

Describe the digestion of proteins by Exopeptidases

A

Hydrolyse terminal peptide bonds

removing a single amino acid from proiten

50
Q

Describe the digestion of proteins by Dipeptidases

A

Hydrolyse the peptide bond between a dipeptide ( = 2 amino acids)
Often membrane bound ileum

51
Q

Describe the mechanisms for co-transport involving Sodium ions and Glucose

A
  1. Sodium ions actively transported out of epithelial cells lining the ileum, into the blood, by the sodium-potassium pump.
    - Creating a concentration gradient of sodium (higher conc. of sodium in lumen than epithelial cell)
  2. Sodium ions and glucose move by facilitated diffusion into the epithelial cell from the lumen, via a co-transporter protein
  3. Creating a concentration gradient of glucose – higher conc. of glucose in epithelial cell than blood
  4. Glucose moves out of cell into blood by facilitated diffusion through a protein channel
52
Q

What is the role of micelles in the absorption of lipids

A

Monoglycerides and fatty acids diffuse out of micelles
Into epithelial cell due to being lipid soluble
Triglycerides remade which aggregate into gloubles
Coated with proteins
Leave via exocytosis and enter lymphatic vessels
Return to blood circulaiton

53
Q

What is a mass transport system?

A

A system Required to carry substances between exchange surfaces and cells in the body

54
Q

Describe the circulatory system

A

Closed double circulatory system

Blood passes through the heart twice for each complete circulation of the body

55
Q

Why is the circulatory system important for animals?

A

Prevents mixture of oxygenated and deoxygenated blood → efficient delivery of oxygen and glucose for repsiration

Blood can be pumped at higher pressure → effeicent gas exchange

56
Q

State and describe the blood vessels in the heart

A

Blood vessels entering and leaving heart:
Aorta – takes oxygenated blood from heart → respiring tissues

Vena cava – takes deoxygenated blood from respiring tissues → heart

Pulmonary artery – takes deoxygenated blood from the heart → lungs

Blood vessels entering and leaving kidneys:

Renal arteries – take deoxygenated blood → kidneys

Renal veins – take deoxygenated blood to the vena cava from the kidneys

57
Q

What is the role of the coronary arteries?

A

Deliver oxygenated blood to cardiac muscle

58
Q

How do the atrioventricular valves relate to heart function?

A

Prevent backflow of blood from ventriles to atria

59
Q

How do the semi-lunar valves relate to heart function?

A

Prevent backflow of blood from artieries to ventricles

60
Q

How do the thickness of the walls of the heart relate to its function?

A

Left
Thicker musclar wall
Higher blood pressure
Oxygenated blood has to travel greater distance

Right 
Thinner muscular wall 
lower blood pressure 
Travel smaller distance to lungs 
where high pressure could damage alveoli
61
Q

Describe the structure of the arteries

A

Thick smooth muscle → contract to control blood flow

Elastic muscle layer – stretch and recoil when contraction of ventricles occurs; even out blood pressure

Thick wall → high pressure to with stand

Narrow Lumen → increases and maintains high blood pressure

62
Q

What is the role of the artieies

A

Carry blood from heart to rest of body at high temperatures

63
Q

What is the role of the arterioles?

A

Division of arteries to smaller vessels which can direct blood to different capillaires

64
Q

Describe the structure of arterioles

A

Thicker muscle layer than arteries → contracts to reduce blood flow
→ relaxes to increase blood flow

Thinner elastic later as lower pressure

65
Q

What is the role of veins?

A

Carry blood back to the heart under low pressure

66
Q

Describe the structure of the veins

A

Wider lumen
Little elastic and muscle tissue
Valves → to prevent back flow of blood
Contraction of skeletal muscles squeezing veins → maintaining blood flow

67
Q

Explain the structure of capillaries and the importance of capillary beds as exchange surfaces

A

One cell thick → short diffusion pathway so rapid diffusion

Capillary bed is made of a large network of (branched) capillaries l (thin) = Increase surface area (to volume ratio) → rapid diffusion

Narrow lumen → reduces flow rate so more time for diffusion

Capillaries are close to tissues → short diffusion pathway

68
Q

What is tissue fluid?

A

The fluid surrounding cells that allows materials to be exchanges between blood and cells

69
Q

Why is tissue fluid important?

A

Provides to respiring cells (water,oxygen,glucose,amino acids etc.)

Enables waste substances to move back into the blood (exp. Urea/lactic acid/carbon dioxide)

70
Q

Describe the formation of tissue fluid

A

The formation of tissue fluid.
Starts at the arteriole end of the capillary
There is high blood pressure going from arteriole to capillary
Higher hydrostatic pressure inside capillaries than tissue fluid
Forces fluid to move out off capillary
Large plasma proteins remain in the capillary ( red blood cells + platelets)

The return of tissue fluid.
Surrounding tissue fluid at venule end
Hydrostatic pressure is low at venous end as fluid leaves capillary
In capillary, lower water potential ,as large proteins remained in the blood, than tissue fluid
Water enters the capillaries by osmosis back down a water potential gradient
Excess water will be absorbed by the lymphatic system (lymp capillaries)
Returned to the circulatory system

71
Q

What occurs in Atrial Systole?

A 
Contraction of atrial walls 
Decreasing volume (in atria)
Increasing pressure (in atria)
Atrioventricular valves = open due to higher pressure in atria 
Blood enters ventricles 
Ventricles relaxed
72
Q

What occurs in Ventricular systole?

A

Atria relaxes
Ventricles contract (walls)
Increasing pressure (in ventirlce)
Decreasing volume (in ventricle)
Semi-lunar valves = open due to higher pressure in the ventricles than arteries (aorta +pulmonary artery)
Atrioventricular valves are shut + closed due to higher pressure in ventricles than atria
Blood pushed out of heart through arteries

73
Q

What occurs in Diastole?

A

Atria and ventricles relax
Increasing volume and decreasing pressure inside chambers
Veins fill atria with blood (slight increase in atrial pressure)
Passive flow of blood into ventricles
Atrioventricular valves = open due to higher pressure inside atria
Semi-lunar valves = closed as pressure inside arteries is higher than ventricles

74
Q

What is the equation of cardiac output?

A

Stroke volume (cm3) x heart rate (BPM)

75
Q

What is cardiac output?

A

Amount of blood pumped out of the heart per minute

76
Q

What is the stroke volume?

A

Volume of blood pumped by the ventricles in each heart beat

77
Q

How can an atheroma (build up of fatty acids) result in a heart attack?

A

Atheroma causes narrowing of coronary arteries

Restricts blood flow to heart muscle supplying oxygen/glucose/etc.

Heart anaerobically respires → less ATP→ not enough energy for heart to contract

Lactate produced damages heart tissue

78
Q

What is a risk factor?

A

Increases probability of getting disease

79
Q

What are risk factor of Cardiovascular disease?

A
  • Age
  • Diet high in salt or saturated fat
  • High consumption of alcohol
  • Stressful lifestyle
  • Smoking cigarettes
  • Genetic factors
80
Q

How can high blood pressure increase the risk of atheroma?

A

Increases risk of damaging the endothelium of artery wall

Increase risk of atheroma

Cause blood clots (thrombus)

81
Q

Describe the structure of Haemoglobin

A

No nucleus
Bioconcave shape
Quaternary structured protein
Each polypetide chain contains a Haem group containting an Iron ion (Fe2+) which combines with oxygen

82
Q

How is oxygen is loaded, transported and unloaded in the blood

A
  • Haemoglobin in red blood cells transports oxygen (as oxyhaemoglobin)
  • Haemoglobin can carry 4 oxygen molecules – one at each Haem group
  • In the lungs, at a high pO2, haemoglobin has a high affinity for oxygen → oxygen readily loads with haemoglobin
  • At respiring tissues, at a low pO2, oxygen readily unloads from haemoglobin
  • Also, concentration of CO2 is high, increasing the rate of unloading
83
Q

Describe the Oxyhamoglobin dissociation curve

A

At high partial pressure (high conc. Of 02), haemoglobin will be completely saturated

At low partial pressure ( low conc. Of oxygen), unloading of oxygen as Haemoglobin less saturated

84
Q

Why is there a s shape curve on Oxyhaem dissociation curve

A

Cooperative nature of oxygen binding

Haemoglobin has low affinity → hard for 1st oxygen to bind
So from 0% saturation, the increase in partial pressure results in slow increase in saturation = Shallow gradient

After 1st oxygen, tertiary shape changes (conformational change) so easier for further oxygen to bind
% saturation rate increases as partial pressure increases —> steep gradient

After 3rd oxygen binding, shape of haemobglobin changes so harder for other molecules to bind
So at high partial pressure, rate of saturation decreases

85
Q

What is the bohr effect?

A

When high Carbon dioxide concentration causes haemoglobin curve to shift to the right

86
Q

Explain the effects of carbon dioxide concentration on the dissociation of oxyhaemogloboin curve

A

Rate of respiration is high → releases carbon dioxide
(lowers PH) Tertiary shape of haemoglobin changes
reduces haemoglobin affinity for oxygen
Increase rate of unloading oxygen
More oxygen provided for muscle/respiring tissues (aerobic)
Oxygen dissociation curve shifts to the right

87
Q

Describe the oxyhaemoglobin curve for fetus

A

Curve shifted left
Has higher affinity for oxygen
More oxygen associates with haemoglobin more at lower partial pressure

88
Q

Describe the oxyhaemoglobin curve for birds (exp. Dove)

A

Curve shifted to right
Has lower affinity for oxygen
Oxygen dissociates more readily to respiring cells at a higher partial pressure
Associates less readily
Faster metabolism → high rate of respiration = oxygen needed

89
Q

What is the cohesion tension theory?

A

How water moves up the xylem against gravity via the trasnpiration stream

90
Q

Explain the cohesion-tension theory of water in the xylem

A
  • Water evaporates from the leaves via the (open) stomata due to transpiration (stream)
  • Reducing water potential in the cell and increasing water potential gradient
  • Water drawn out of xylem
  • Creating tension
  • Cohesive forces between water molecules pull water up as a column
  • Water is moving up, against gravity
  • Water is also cohesive so sticks to the edges of the column
91
Q

What are the adaptions of the xylem?

A

Hollow → no cytoplasm/nucleus to slow water flow
Thick cell walls with lignin → les likely to collapse under low pressure
Narrow lumen increases height water can rise

92
Q

What is the xylem?

A

The tissue that transports water in the stem and leaves of plants

93
Q

What is the phloem?

A

The tissue that transports organic substances in plants

94
Q

Explain the mass flow hypothesis for the mechanism of translocation in plants

A

Translocation:
- assimilates from source to sink

At the source:

  • High concentration of solute
  • Active transport loads solutes from companion cells to sieve tubes of the phloem
  • Lowering the water potential inside the sieve tubes
  • Water enters sieve tubes by osmosis from xylem
  • Increasing pressure inside sieve tubes at the source end

At the sink:

  • Low concentration of solute
  • Solutes removed to be used up e.g. enzymes hydrolyse
  • Increasing the water potential inside the sieve tubes
  • Water leaves tubes via osmosis
  • Lowering pressure inside sieve tubes

Mass flow:

  • Pressure gradient from source to sink
  • Pushes solutes from source to sink
  • Solutes used or stored at the sink e.g. respiration
95
Q

What are the adaptations of the phloem

A
  • sieve tube elements have no nucleus and few organelles

- existence of companion cell → carry out living functions for sieve cells

96
Q

What you can use to investigate transport in plants

A

Use of tracers
Placing radioactive tracer
Organic substances undergo translocation
Auto radiography - film turns black where radioactive substance present
Can identify where radioactive substance has moved via translocation from source to sink
Can show this over time by taking auto radiography at different times

97
Q

How can you use a potometer in terms of plant investigation?

A

Estimates the transpiration rate by measuring water uptake

98
Q

What are the different factors affect transpiration rate?

A

Light
Temperature
Humidity
Wind

99
Q

How does light affect the transpiration rate?

A
  • The higher the light intensity, the faster the transpiration rate (positive
    correlation)
  • Because stomata open in light to let in CO2 for photosynthesis
  • Allowing more water to evaporate faster
  • Stomata close when it’s dark so there is a low transpiration rate
100
Q

How does temp affect the transpiration rate?

A
  • The higher the temperature, the faster the transpiration rate (positive
    correlation)
  • Water molecules gain kinetic energy as temperature increases
  • Move faster
  • Water evaporates faster
101
Q

How does Humidty affect the transpiration rate?

A
  • The lower the humidity, the faster the transpiration rate (negative correlation)
  • Because as humidity increases, more water is in the air so it has a higher water
    Potential
  • Decreasing the water potential gradient from leaf to air
  • Water evaporates slower
102
Q

How does wind affect the transpiration rate?

A
  • The windier, the faster the transpiration rate (positive correlation)
  • Wind blows away water molecules from around the stomata
  • Decreasing the water potential of the air around the stomata
  • Increasing the water potential gradient
  • Water evaporates faster

AQA A Level Biology (9 decks)

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